Reversing mechanism for engines



April 18, 1944. M. ESSL 2,346,737

REVERSING MECHANISM FOR ENGINES Filed Aug. 18, 1941 2 Sheets-Sheet l Apri 18, 1944. v I ss 2,346,737

' REVERSING MECHANISM FOR ENGINES Filed Aug. 18, 1941 2 Sheets-Sheet 2 For-ward Opera tzon Re verse Opera izarz Patented Apr. 18, 1944 aavnasmc MECHANISM FOR enemas Max Essl, Swarthmore, Pa., assignor td'lhe Baldwin Locomotive Works, a corporation of Pennsylvania Application August 18, 1941, Serial No. 407,381

Claims.

This invention relates generally to engines of the reciprocating piston and cylinder type and more particularly to an improved mechanism for facilitating forward or reverse operation of internal combustion engines.

Reversible engines have various applications,

especially in tug boats where a high degree of maneuverability may require frequent forward and backward operations, although reversible engines are applicable in boats of any kind as well as in other fields.

Various reversing methods especially for inter; nal combustion engines have heretofore been proposed and used some of which include th rather cumbersome arrangement of employing a reversing gear interposed between the engine and ship propeller shaft, while other arrangements employ two sets of cams for operating the engine valves, one set of cams being adapted for forward rotation of the engine and the other set for reverse rotation. To shift from one set of cams to the other first requires that the cams and cam followers are entirely clear of each other which I in certain instances has heretofore been accomplished by dropping the camshaft or by bodily lifting the entire push rod and its associated cam follower so that the cams are free and'clear of the cam followers whereby the camshaft may be then shifted axially to bring the second set of cams into alignment with the cam. followers whereupon the cam is raised or the push rod bodily lowered, as the case may be, into its nor-' mal operative position. .While these arrangements have the advantage that the two sets of cams may be placed close to each other thereby being conducive to a short compact engine, yet they do have the disadvantage. of requiring expensive mechanism or a specially designed engine for allowing the camshaft to be bodily dropped or of bodily lifting the push rods out of their opera tive position. To overcome these diificultie's it has been heretofore proposed in another arrangement to have the two sets of cams sumciently i.

spaced apart axially so that the entire cam surfaces may be connected by gradually inclined surfaces which act as ramps or bridges over which the' cam followers slide from one set of cams to the other without any possibility of the followers striking the cam sides. This involves an excessively long camshaft to accommodate the gradual ramp surfaces and consequently the engine cylinders must be spread apart far enough to provide this space or else this type of reversing arrangement cannot be used.

It is an object of my invention to provide an improved reversing mechanism that will permit the two sets of cams to be spaced close together without the need of inclined ramp surfaces be-- tween the two sets of cams and yet will eliminate the necessity of bodily lifting the entire push rod or of dropping the camshaft during shifting from one set of cams to the other.

Another object is to provide an improved reversing mechanism for lifting the cam follower without bodily lifting the entire push rod structure which would require unseating the valve as the rod rises.

A still further object is to provide an improved reversing mechanism whereby the effective length of the push rod structure which is from the cam follower to the valve rocker arm may be shortened in a simple, expeditious and efiective manner so as to lift thecam follower away from the cams and thereby allow axial shifting of the camshaft from one set of cams to the other.

Another object is to provide my improved reversing mechanism in combination with an automatic valve tappet clearance take-up. In the specific aspect of the invention disclosed herein, this improvedcombination of functions is embodied in a single device so constructed and arranged that these dual functions may be ef-' fectively performed by elements common to each.

Other objects and advantages will be more apparent to those skilled in the art from the following description of the accompanying drawings in which:

Fig. 1 is a fragmentary vertical section through the cylinder end of a reversible internal combustion engine embodying my invention; and

Fig. 2 is an enlarged sectional view of my improved mechanism taken substantially on the line 22 of Fig. l with certain parts shown in elevation for purposes of clarity.

In the particular embodiment of the invention, I have disclosed the same in connection with an internal combustion engine preferably of the Diesel type, although the invention may be employed with other types of engines which may have as many cylinders as desired in line or radially positioned. Hence, the present illustration will serve as a basis for these well-known types of engines which broadly comprise a cylinder i and piston! connected to a crankshaft (not shown) by a usual connecting rod 3. Any suitable type of cylinder head generally indicated at 4 openedby rocker arm I pivotally supported at 9 upon a suitable bracket 9 although as is well known certain engines have cams acting directly on the valve stem. which is equivalent to a push rod. A camshaft i is suitably journalled in a housing II and is driven by the usual crankshaft in any usual manner by gears or chains. The camshaft shown in Fig. 2 has two sets of cams l2 and I3 for each valve 5, these sets being spaced relatively close to each other without any inclined connecting or ramp'surface between the same. One set of cams I2 is for forward operation and the other set l3 for reverse operation. While the drawings hereof illustrate only one valve, it will, of course, be understood that as many valves are employed as may be necessary in the operation of any particular type of engine. Ordinarily one exhaust valve and one intake valve is required for each cylinder and under such circumstances each valve has its own push rods and sets of forward and reversing cams.

A cam follower specifically a roller i4 is suitably journalled as at M", Fig. 2, in a push rod sleeve l5 which is vertically guided in a stationary guide housing Hi, this housing being suitably secured as by bolts I! to the cam housing II. The sleeve and roller are prevented from rotating by a usual shaft extension l4a disposed within a vertical groove Mb. The sleeve I5 is operatively connected in an improved manner to a push rod l8 whose upper end is connected to rocker arm 1 preferably through a spherical connection l9. The push rod is preferably enclosed within a tubular housing whose upper end is connected to a housing 2| and whose lower end issuitably connected to an extension 22 of the guide housing l6. Lubricating oil may be circulated in a welllznown manner over the rocker arm and downwardly through push rod housing 20.

To axially shift camshaft ill from its forward to reverse position or vice versa, it is necessary to lift roller l4 above the maximum elevation of the cam surface of the adjacent cam such as l2, Fig. 2, whereupon the camshaft can be axially shifted through usual means (not shown) to bring cam l2 into alignment with roller l4. The roller is then lowered into engagement with cam l2. Instead of bodily lifting the engine push rod l8 in order to lift roller I4, I have provided improved collapsing mechanism adapted to shorten the dis? tance between roller l4 and connection 19 with rocker arm I. In addition to this improved mode of operation, I can, if desired, accomplish the further function in the same collapsing device of automatically taking up valve tappet clearance. This improved device consists, as shown in Fig. 2, of a spring 25 seated at its lower end on a ring 26 which, in turn, is supported upon an annular shoulder of housing it while the upper end of the spring is seated against a flange 21 formed on the upper end of sleeve l5 thereby normally biasuppermost end of sleeve l5 and in normally spaced relation to socket 32 for the purpose of preventing accidental displacement thereof out of the sleeve. So long as a predetermined pressure is maintained within cylinder 29 action and reaction expansion forces on socket 32 and on the lower end of cylinder 29 will cause body l5 and roller 14 to be held in a downward position against the action of spring 25 but when fluid pressure within cylinder 29 is relieved, then spring 25 will bodily lift sleeve l5 and its roller l4. Cylinder 29 and sleev l5 will move upwardly relative to plunger 30 and socket 32. Th expansion action of the push rod is broadly a restoring operation after collapse of the push rod.

To control fluid pressure within'cylinder 29 as well as to automatically take up valve tappet clearance, I provide a ball check valve 35 normally seated on its under side to allow free upward flow of pressure fluid through a port 39 and thence through a port 31 into cylinder 29. Fluid pressure is supplied preferably by a constant pressure pump 38 from a storage tank 39 and thence through a three-way control valve 40 to a chamber 4| formed in sleeve l5 and communicatin through a port 42 with a check valve control cylinder 43 from whence the fluid can flow upwardly past ball check 35 in the manner above mentioned to resist the collapsing action of spring 25. Hence as the cam, such as l3, Fig. 2, moves sleeve l5 upwardly fluid within cylinder 29 will be trapped so as to cause plunger 35 and push rod seat 32 to move upwardly with sleeve l5 as a unit therewith. On the down stroke of sleeve l5 the usual valve spring '6, Fig. 1, will cause push rod l8 to maintain plunger 30 in firm contact with the trapped oil in cylinder 29 and accordingly maintain the usual operative contact between roller l4 and its cam. This arrangement insures automatic take-up of th valve tappet clearance betweenthe fluid pressure supplied to chamber 4| will always exert a force within cylinder 29 sufllcient to maintain roller l4 in contact with its cam, this fluid pressure of course being less than the force exerted by valve spring 6 and accordingly preventing the fluid pressure from creating an excessive elongation of the distance between seat l9 and roller l4. Excessive accumulation of oil within cylinder 29 is also prevented by reason of a small "amount of leakage upwardly between plunger 30 and its cylinder wall 29. Hence by ing this sleeve upwardly so as to tend to lift roller l4 away from its cam. To restrain the upward biasing force of spring 25 and thereby maintain roller l4 in normal operative contact with its cam, there is provided an internal collapsing control mechanism having a body 28 fixed at its lower end to sleeve l5 so as to form a unitary structure therewith. The upper end of this body is provided with a cylinder 29 in which a plunger 30 is normally moved upwardly by fluid pressure within the cylinder thereby forcing the upper flanged head ill of the plunger against a push rod socket 32 which is slidably disposed within a bore 33 of sleeve IS. A ring .34 is supported in the controlling the volume of pressure fluid supplied through valve 40 the desired balance between supply and leakage may be maintained to insure normal operation of the push rod with its desired clearance. To compensate for the combined weight of push rod l8, seat 32 and plunger 30, a spring 45 is interposed between body 22 and the upper flanged end 3| of plunger 30.

To collapse the push rod by spring 25 I employ means for lifting ball check 35 with consequent discharge of fluid from cylinder 29. This means comprises a piston 41 normally biased upwardly by a spring 48 seated upon a washer 49 which is upported by the lower end of body 28. A pin 50 carried by piston 41 is adapted upon release of pressure in cylinder 43 to push ball 35 away from its lower seat. Release of fluid pressure in cylinder 43 is controlled by three-way valve 40 which when turned to its exhaust position will discharge fluid from chamber 4| while at the same time shutting off fluid pressure supplied from pump 38. Release of pressure within chamber 29 will immediately permit collapsing spring 25 to'raise sleeve l5 and roller l4 while at the same time maintaining push rod I8 in contact with its con nection Hi. When roller I4 is thus raised cam I may be moved axially to bring the second cam, such as 12, into alignment with roller M whereupon valve 40 is turned to close the exhaust and connect pump 38 with chamber 4| so as to move piston'fl downwardly whereupon fluid pressure axially to bring one or the other of said sets of cams into operative relation to said push rod tively operated by forward or reverse sets of cams lifts ball check 35 to fill cylinder 29 thus lowering sleeve [5 into engagement with its cam. The foreoing collapsing operation is in effect a collapse of the effective length of the valve "push rod structure which broadly extends from roller M to connection l9 while the subsequent expansion of the push rod is broadly a restoring action.

From' the foregoing disclosure, it is seen that I have provided an improved combination of elements having a novel mode of operation for allowing the camshaft to be shifted axially from one set of cams to another set without the need of either bodily lifting the entire push rod structure or of droppingthe camshaft. and at'the same time I am able to utilize my improvedcombination to in sure automatic valve tappet take-up. The device is so constructed and arranged that it is relatively compact and can be readily incorporated in new or existing engines and can be operated in an easy and simple manner with minimum cost in operation, maintenance and initial construction.

It will of course be understood that various changes in details of construction and arrangement of parts may be made by those skilled in the art without departing from the spirit of the invention as set forth in the appended claimsv I claim:

1. A reversing mechanism for internal combustion engines of the type having a valve selectively operated by forward or reverse sets of cams on a camshaft which is axially shiftable to bring either set of cams into operation comprising, in combination, a push rod structure interposed between said camshaft and valve, and means including a hydraulically controlled piston and cylinder movable with the push rod structure'for collapsing the same thereby to move a portion thereof out of operative relation to said cams operated by forward or reverse sets of cams on a camshaft which is axially shiftable to bring either set of cams into operation comprising, in combination, a collapsible push rod structure interposed between said camshaft and valve, yieldable means for exerting a collapsing force on said push rod structure, means for resisting said yieldable collapsing means, and means for removing said resisting action so that consequent collapse of said push rod structure removes it from an operative relation to said camshaft thereby allowing the latter to be shifted axially to"bring another set of cams in alignment with said push rod structure whereafter restoration of the push rod structure to its normal position brings the same into operative relation to the camshaft.

on a camshaft which is axially shiftable to bring either set of cams into operation comprising, in combination, a collapsible push rod structure interposed between said camshaft and said valve, yieldable means for biasing said push rod structure in one direction, hydraulic means for biasing said structure in an opposite direction, and means for releasing or actuating said hydraulic means so as to effect collapse or restoration of said push rod structure, said camshaft being axially shiftable to a selected set of cams when said push rod structure is collapsed and the collapsed push rod structure being restored to its operative condition when the selected cam is in position.

' 5. A reversing mechanism for internal combustion engines of the type having a valve selectively operated by forward,'or reverse sets of ains on a camshaft which 'is .axially shiftable to bring either set'of cams into operation comprising, in

- combination, a push rod, a cam follower guide sleeve adapted to be actuated by one or the other of said sets of cams, a push rod seat slidably supported on said sleeve, means for normally maintaining said seat and sleeve in a substantially predetermined axial relation during normal cam operation of the push rod and sleeve, and means for relatively axially moving said seat and sleeve to reduce the combined effective length of said push rod and sleeve thereby allowing the cam follower to have clearance-with the camshaft so that the latter may be shifted axially to bring one or the other of said sets of. cams into operative relation to the cam follower.

6. A reversing mechanism for internal combustion engines of the type having a valve selectively operated by forward or reverse sets of cams on a camshaft which is axially shiftable to bring either 'set of cams into operation comprising, in

' combination, a push rod structure interposed between said camshaft and valve, means for automatically taking up clearance between said valve and camshaft, and means including said auto- 3. A reversing mechanism for internal combusmatic means "as a part thereof for collapsing said push rod structure so as to allow said camshaft to be shifted axially to bring one or the other of said sets of cams into operativerelation with said push rod structure.

.7. A reversing mechanism for internal combustion engines of the type having a valve selectively operated by forward or reverse sets of cams on a camshaft which is axially shiftable to bring either set of cams into operation comprising, in combination, a push rod structure'interposed between said camshaft and valve, mechanism formed as a part of said push rod structure for taking up clearance between the valve'and camshaft automatically upon occurrence of clearance, and means for rendering said take-up inoperative and for collapsing said push rod structure so as to render it free of said camshaft automatically when said clearance take-up is rendered inoperative whereby said camshaft may then be shifted axially to bring one or the other of said sets of cams into alignment with said push rod structure and thereafter said clearance take-up means is rendered operative to restore said push rod structure to its normal operative condition.

8. A reversing device for internal combustion engines adapted to be interposed between a camshaft and a valve or an engine comprising, in combination, a member having a cam follower at one end and means at its other end for connec- 'tion to a push rod, said push rod connection having axially slidable engagement with said member, yieldable means for effecting said axial slidable movement, and variably controlled hydraulic means adapted during the presence of hydraulic pressure to resist said yieldable means so as to prevent said relative axial movement and upon external exhaust of fluid pressure to allow said relative movement.

9. The combination in a reversing device for collapsing a push rod structure of an internal combustion engine comprising a cam follower sleeve having acam follower at its lower end, a push rod seat slidably supported at the upper end 01 said sleeve, a cylinder located internally of said sleeve, a plunger disposed within said cylinder for moving said push rod seat away from said cam follower, means for moving said sleeve in a direction toward said seat thereby to collapse follower, means for moving said sleeve in a direction toward said seat thereby to collapse the push rod structure, means for hydraulically controlling movement of said plunger in its cylinder thereby determining the relative movement between said sleeve and push rod seat, and yieldable means interposed between said cylinder and plunger to 20 resist the weight of any parts acting downwardly on said plunger.

MAX ESSL. 

